1. The Field of the Invention
The present invention relates to nanocatalysts for use in improving the combustion properties of fuels. In particular, the present invention relates to nanocatalysts with a desired crystalline structure for improving combustion of fuels.
2. Related Technology
Carbon-containing fuels typically combust to yield mainly carbon dioxide and water as the major products of combustion. Due to incomplete combustion, however, other more harmful molecules can be formed, such as carbon monoxide (CO), hydrocarbons and soot. Impurities in the fuel can also yield significant quantities of ash, SOx and NOx. Due to increased environmental awareness and stricter governmental guidelines, there are ongoing efforts to reduce the release of harmful emissions into the environment.
Coal combustion is a major source of energy for the production of electricity throughout the world. Coal is a good source of energy because of its high energy to weight ratio and its great abundance. The use of coal, however, is increasingly under scrutiny because of environmental concerns. Among the known environmental difficulties with coal combustion is the production and emission of NOx compounds, such as NO, N2O, and NO2. NOx compounds can be very harmful to human health and are known to produce undesirable environmental effects such as smog.
Government regulations require emission from coal burning to be monitored and controlled. Controlling NOx emissions has become increasingly difficult as government regulations continue to lower the allowable level of NOx and other pollutants that can be released into the environment. The requirement for reduced pollutants from coal-fired power plants has led to a demand for suitable new technologies.
In a coal fired power plant, there are two principle sources of NOx formation: fuel NOx and thermal NOx. Fuel NOx is NOx that forms from nitrogen found in the fuel, whereas thermal NOx is formed from other sources of nitrogen such as nitrogen in the air. About 80% of NOx emissions from coal combustion are produced from fuel nitrogen.
One method used to reduce pollutants during coal combustion focuses on removing NOx from power plant flue gas. For example, NOx emitted in flue gas can be removed using selective catalytic reduction (SCR), which converts NOx compounds to nitrogen gas (N2) and water. However, this type of NOx control method is expensive, in part, because of the required capital investment. The cost of these technologies and increasingly stringent government regulations have created a need for less expensive technologies to reduce NOx emissions from coal combustion.
Another method of reducing NOx emissions is to remove coal nitrogen from the coal material by converting it to N2. Recently, researchers have discovered that iron-based catalysts can assist in releasing fuel nitrogen from coal. One problem with dispersed iron-based catalysts used to reduce pollutants during combustion is the amount of metal that needs to be applied to the fuel to obtain desirable results. If too much metal is added to the fuel, the presence of the metal can undesirably affect combustion performance of the fuel and/or negatively affect the composition of combustion products such as fly ash. In addition, high metal loadings can make the catalyst cost-prohibitive for many commercial applications.
There is a need to improve the performance of dispersed metal catalyst for reducing pollutants generated during combustion. Even small improvements in catalyst performance can have a significant impact on the amount of catalyst used for a particular application and/or the amount of pollutants removed from the combustion gases.